Voltage supply for radio proximity fuze

ABSTRACT

1. In a radio-controlled proximity fuze in which a high frequency signal is generated and radiated and received after reflection from a target approached by said fuze and a beat frequency signal derived from the two signals controls the detonation of said fuze, an electrically-actuated detonator adapted to initiate the detonation of said fuze, a gas-filled discharge tube adapted to actuate said detonator when ionized, means responsive to said high frequency and said reflected signals to bias said tube below its starting voltage, and means responsive to a selected amplitude and number of cycles of said beat frequency signal for ionizing said gas-filled tube.

United States Patent [191 Jacob 1 July 22,1975

[ VOLTAGE SUPPLY FOR RADIO PROXIMITY FUZE [75] Inventor: Carlyle W. Jacob, Rochester, NY.

[73] Assignee: The United States of America as represented by the Secretary of the Navy, Washington, DC.

221 Filed: Mar. 12, 1951 211 Appl. No.: 215,043

OTHER PUBLICATIONS Huntoon et al., Generator-Powered Proximity Fuze Electronics, December 1945, pages 98-103 inclusive 343-347.

I-Iinman et al., Radio Proximity Fuze Design," Bureau of Standards Research Paper RP1723, Vol. 37, July 1946, 18 pages 343-347.

Primary ExaminerT. H. Tubbesing Attorney, Agent, or FirmR. S. Sciascia; J. A. Cooke EXEMPLARY CLAIM 1. In a radio-controlled proximity fuze in which a high frequency signal is generated and radiated and received after reflection from a target approached by said fuze and a beat frequency signal derived from the two signals controls the detonation of said fuze, an electrically-actuated detonator adapted to initiate the detonation of said fuze, a gas-filled discharge tube adapted to actuate said detonator when ionized. means responsive to said high frequency and said refiected signals to bias said tube below its starting voltage, and means responsive to a selected amplitude and number of cycles of said beat frequency signal for ionizing said gas-filled tube.

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(Ittorneg 5' l0 VOLTAGE AT PLATE 0/ TF/ODE /6, IN VOLTS VOLTAGE SUPPLY FOR RADIO PROXIMITY FUZE This invention relates to radio apparatus and in particular to radio-controlled proximity fuzes for projectiles.

Size and weight limitations for radio proximity fuzes are fixed by military necessity. The radio proximity fuze must fit existing projectiles using the same fuze well as a mechanical fuze and further must not alter the ballistic characteristics of the projectile. The space requirements for fuzes for guns as small as 75 millimeters are particularly stringent as every cubic inch of space required for the fuze means that much less explosive for the projectile. Consequently any reduction in the size and weight of the components of the fuze without sacrifice in performance is highly desirable.

In order to provide the necessary plate, filament and grid bias voltages, the deferred action, or reserve, type batteries for radio proximity fuzes for artillery shells have heretofore been manufactured with separate A, B and C voltage sections. Elimination of any one of the sections will allow reduction in the size and weight of the fuze. Furthermore, both noise voltage in the output of the battery and decay of battery voltage with time after firing of a projectile are potential causes of premature detonations, and elimination of any one of the battery sections will reduce the probability of premature detonations from such causes.

It is the principal object of the invention to provide a radio-controlled proximity fuze for artillery projectiles in which it is unnecessary to include a grid bias C voltage section in the deferred action type battery of the fuze.

The object of the invention is attained by rectifying a portion of the radio frequency energy of the oscillating detector of the fuze to derive a voltage to bias the thyratron below its starting, i.e., critical firing, voltage. in the preferred embodiment of the invention an electron tube having at least three electrodes is utilized both as a conventional avc (automatic volume control) diode" for the beat frequency signal at which the amplifier is peaked and as a rectifier for radio frequency energy to develop the desired voltage to bias the grid of the thyratron. A small portion of the radio frequency energy from the oscillating detector of the fuze is rectilied in the cathode-plate circuit of a conventional triode, and the rectified voltage is applied across a suitable voltage dividing network including a nonlinear impedance to provide a substantially constant grid bias voltage for the thyratron. The output of the amplifier of the fuze is coupled to the grid-cathode circuit (which is used as an avc diode) of the triode to limit positive pulses and to develop avc bias, and a radio frequency choke coil is inserted between the output of the amplifier and the triode grid to isolate the radio frequency energy.

These and other objects, advantages and novel features of the invention will be apparent from the following description and accompanying drawings in which:

FIG. I is a diagram of the portion of the circuit which provides grid bias voltage for the thyratron in a radio fuze constructed in accordance with the principles of my invention; and

FIG. 2 is a curve illustrating the action of the nonlinear impedance of the circuit shown in FIG. 1 in stabilizing the grid bias voltage at a substantially constant value regardless of fluctuations of the rectified radio frequency voltage.

As is well known in the art, a radio proximity fuze is essentially an autodyne, or oscillating, detector which includes an oscillating detector tube 10, a coil 11, and a transmitting antenna 12 as shown in FIG. 1 of the drawings. The transmitting antenna 12 also receives radiated energy which strikes a target and is reflected back, and the operating signal is furnished by the combination of a wave reflected from the target with the local oscillator voltage. The beat note, or difference between the local oscillator frequency and the frequency of the reflected wave, is the signal used to detonate the fuze when it approaches the reflecting target at a preselected velocity and when it is close enough for the reflected wave to have sufficient amplitude. The beat signal appears across the load in the plate circuit of the oscillator detector tube 10 and is filtered and amplified in an amplifier I3 utilizing pentode tubes and having a number of stages depending upon the gain required. Selective filter circuits (not shown) in the amplifier 13 by-pass the radio frequency components of the combined signals to ground and peak the amplifier at the beat frequency. The filters and the stages of amplification are well known in the art and do not constitute a part of my invention, and in order to facilitate the better understanding of the invention the amplifier 13 is shown in block form in the drawings. In conventional radio fuzes the output of the last amplifier stage is capacitively coupled to the grid of a thyratron 14, and upon the application of a strong enough signal the thyratron 14 fires and discharges a capacitor through an electric detonator (shown in block form) in a well known manner.

In the amplifiers of many fuzes heretofore manufactured, the plate electrode of the last amplifier stage was coupled to an automatic volume control (avc) diode which acted as a half-wave rectifier having two functions, namely to clip or limit the positive half of single cycle signals and to develop a bias for avc purposes. In many of these fuzes the cathode-grid electrode circuit of a high vacuum tube having three or more electrodes was utilized as the avc diode with the plate electrode of the tube connected to the grid.

In the preferred embodiment of my invention I utilize the cathode-grid circuit of a triode 16 as an avc diode halfwave rectifier for the selectively amplified and filtered beat frequency signal to provide the pulse limiting and to provide the avc bias as described above, and I further utilize the cathodeplate circuit of this same triode 16 as a half wave rectifier for a portion of the radio frequency energy of the oscillating detector to provide the necessary bias voltage for the grid of the thyratron 14. The amplified and selectively filtered output from the last stage of the amplifier 13 is applied to the grid electrode of the triode 16 (which grid serves as the anode of the beat frequency half-wave rectifier avc diode) through a coupling condenser 18 and a radiofrequency choke 19. Resistors 21 and 22 provide a voltage dividing network which determines the avc bias voltage applied to the first amplifier stage to desensitize the amplifier 13. The effect of the pulse limiting action of the cathode-grid circuit of the triode 16 is to prohibit the thyratron 14 from firing on pulses or on single cycles but to effect only slightly the sensitivity to ripple signals lasting several cycles, e.g., beat frequency plane target signals.

A plane target signal consists of a number of cycles which vary in amplitude and frequency as the projectile approaches the target. Conduction takes place in the grid-cathode circuit of triode 16 when the target signal swings positive, thereby charging coupling condenser 18. When the target signal swings negative, condenser 18 discharges causing condenser 24 and the avc filter condenser 28 to become charged. The time constant of the avc filter including resistor 27 and condenser 28 is long compared to the time constant of the thyratron grid coupling circuit including condenser 24 and the resistance connected between the grid of the thyratron 14 and ground, i.e., resistor 29 in series with a nonlinear impedance 35 to ground. Because of this variation in time constants, many cycles are necessary to produce the negative avc bias voltage, whereas, only a few cycles of a target signal whose amplitude increases during these few cycles will cause condenser 24 to be charged to sufficient voltage and proper polarity to overcome the bias on the grid of the thyratron 14.

The rate of increase of signal amplitude, the number of cycles, and the frequency determine whether the thyratron bias is overcome or whether avc bias is developed to reduce the amplifier gain as in the case when the projectile approaches ocean waves. In the case of reduced amplifier gain because of ocean waves, the target signal amplitude and rate of increase superimposed on the wave signal must be sufficient to cause condenser 24 to be charged to overcome the thyratron bias.

My invention is particularly directed to the use of the cathode-plate electrode circuit of the triode 16 as a half-wave rectifier for radio frequency energy to provide a substantially constant voltage source to bias the grid of the thyratron 14 below the starting voltage. A small portion of the radio frequency power from the cathode of the oscillator tube 11 is by-passed to the plate of the triode 16 through a condenser 31 which discharges on alternate half-cycles to ground through a voltage dividing network including a resistor 33 and a suitable nonlinear impedance 35 such as a symmetrical silicon carbide variator, or a thyrite resistor, characterized by a decreasing resistance as the voltage across the impedance increases. The radio frequency choke 19 between the grid of the triode 16 and the condenser 18 isolates the radio-frequency cathode-plate rectifier circuit from the beat frequency portion of the circuit. 1 have found it convenient to choose components having values to provide a negative voltage of approximately 15 volts at the plate electrode of the triode l6 and approximately 6 volts resistance drop across the nonlinear impedance 35 to bias the grid of the thyratron 14.

FIG. 2 illustrates the effectiveness of the voltage network including the nonlinear impedance 35 in maintaining a substantially constant bias on the grid of the thyratron 14 even if the voltage at the plate of the triode l6 fluctuates over a wide range. It will be noted that with a four megohm resistor 33 in series with the nonlinear impedance 35 to ground, the voltage across the nonlinear impedance 35 will be maintained between and 6 volts even though the rectified radio frequency voltage at the plate of the triode 16 may vary from to l8 /z volts.

It will be apparent from the foregoing description and the drawings that a radio-controlled proximity fuze for artillery projectiles has been described in which with addition of four small electronic components, namely the nonlinear impedance 35., choke coil 19, condenser 31 and resistor 33, it is possible to utilize a deferred action type battery with only A and B sections.

While for the purpose of explaining the invention a specific embodiment has been illustrated and described, it is to be understood that the invention may take other forms without departing from the scope of the appended claims.

I claim:

1. ln a radio-controlled proximity fuze in which a high frequency signal is generated and radiated and received after reflection from a target approached by said fuze and a beat frequency signal derived from the two signals controls the detonation of said fuze, an electrically-actuated detonator adapted to initiate the detonation of said fuze, a gas-filled discharge tube adapted to actuate said detonator when ionized, means responsive to said high frequency and said reflected signals to bias said tube below its starting voltage, and means responsive to a selected amplitude and number of cycles of said beat frequency signal for ionizing said gas-filled tube.

2. A radio proximity fuze of the type which radiates a high frequency signal and utilizes the signal reflected from a target approached by said fuze to detonate said fuze, comprising a source of high frequency signal, means for radiating a portion of the high frequency signal, means for receiving the reflected signal and for combining it with the high frequency signal to derive a beat frequency signal, a firing circuit for the fuze including the anode and cathode of a gas-filled discharge tube having anode, cathode and control grid electrodes, means including a nonlinear impedance between the cathode and the anode of an electron tube for developing from said high frequency and said reflected signals a voltage for biasing the gas-filled tube to its deionized state, and means responsive to a predetermined amplitude and number of cycles of the beat frequency signal for triggering the gas-filled tube.

3. In a radio fuze in which a high frequency signal is generated and radiated and the energy reflected from a target approached by the fuze is received and combined with the high frequency signal to derive a beat frequency signal which after amplification in an amplifier controls the detonation of an electrically-actuated detonator, a gas-filled discharge tube adapted to actuate said detonator when ionized, means including the cathode-grid electrode circuit of an electron tube having cathode, control grid, and plate electrodes for developing a voltage which is a function of the amplitude of said amplified beat frequency signal for controlling the gain of said amplifier, means including the serial arrangement of a linear and a nonlinear impedance in the cathode-plate electrode circuit of said electron tube for developing from said high frequency and said reflected signals a voltage for biasing said gas-filled tube below its starting voltage, high frequency choke coil means in said cathodegrid electrode circuit for isolating said automatic volume control bias developing means from the high frequency bias developing means, and means for coupling the output of said amplifier to the grid of said gas-filled tube.

4. In a radio-controlled promixity fuze having an antenna adapted to radiate and receive radio frequency energy, a detector coupled to said antenna and adapted to oscillate at radio frequency and to detect the difference in frequency between the radiated signal and the signal reflected from a target approached by said fuze, an amplifier peaked at said difference in frequency and adar d to by-pass said radio frequency to ground, an electrically-actuated detonator adapted to initiate the explosion of said fuze, and a grid-controlled gas-filled discharge tube adapted to actuate said detonator when energized; circuit means for providing a voltage for biasing said gas-filled tube below its starting voltage and for providing an automatic volume control bias voltage for said amplifier, including the serial arrangement of a resistance and a radio frequency choke coil in the cathode-grid circuit of an electron tube having cathode, grid, and plate electrodes, the output of said amplifier being coupled to the grid electrode of said electron tube through said choke coil and being capacitively coupled to the control grid of said gas-filled tube, a linear and a nonlinear impedance in series in the cathode-plate circuit of said electron tube, the grid of said gas-filled tube being coupled to the junction of said linear and said nonlinear impedances, and means for coupling a portion of the radio-frequency energy from said oscillating detector across said cathode-plate circuit.

5. In a radio-controlled proximity fuze in which a high frequency signal is generated and radiated and received after reflection from a target approached by said fuze and a beat frequency signal derived from the radiated and reflected signals triggers a gas-filled discharge tube to initiate the detonation of the fuze, means ineluding a rectifier and a nonlinear impedance in the output circuit of said rectifier for deriving from said high frequency and said reflected signals a substantially constant voltage for biasing said gas-filled tube to its deionized state.

6. In a radio-controlled proximity fuze in which a high frequency signal is generated and radiated and received after reflection from a target approached by said fuze and a low frequency signal derived from heterodyning said radiated and reflected signals is amplified in an amplifier and triggers a gas-filled discharge tube to initiate the detonation of said fuze, means including the cathode-plate circuit of an electron tube and a nonlinear impedance in said cathode-plate circuit for deriving from said high frequency and said reflected signals a voltage for biasing the gas-filled tube to its deionized state, means including the cathode-grid circuit of said electron tube for developing a voltage which is a function of the amplitude of said amplified low frequency signal for controlling the gain of said amplifier, and means for isolating said high frequency voltage deriving means from said low frequency voltage developing means.

7. In a fuze in accordance with claim 6 and including means responsive to a selected amplitude and number of cycles of said amplified low frequency signal for ionizing said gas-filled tube. 

1. In a radio-controlled proximity fuze in which a high frequency signal is generated and radiated and received after reflection from a target approached by said fuze and a beat frequency signal derived from the two signals controls the detonation of said fuze, an electrically-actuated detonator adapted to initiate the detonation of said fuze, a gas-filled discharge tube adapted to actuate said detonator when ionized, means responsive to said high frequency and said reflected signals to bias said tube below its starting voltage, and means responsive to a selected amplitude and number of cycles of said beat frequency signal for ionizing said gas-filled tube.
 2. A radio proximity fuze of the type which radiates a high frequency signal and utilizes the signal reflected from a target approached by said fuze to detonate said fuze, comprising a source of high frequency signal, means for radiating a portion of the high frequency signal, means for receiving the reflected signal and for combining it with the high frequency signal to derive a beat frequency signal, a firing circuit for the fuze including the anode and cathode of a gas-filled discharge tube having anode, cathode and control grid electrodes, means including a nonlinear impedance between the cathode and the anode of an electron tube for developing from said high frequency and said reflected signals a voltage for biasing the gas-filled tube to its deionized state, and means responsive to a predetermined amplitude and number of cycles of the beat frequency signal for triggering the gas-filled tube.
 3. In a radio fuze in which a high frequency signal is generated and radiated and the energy reflected from a target approached by the fuze is received and combined with the high frequency signal to derive a beat frequency signal which after amplification in an amplifier controls the detonation of an electrically-actuated detonator, a gas-filled discharge tube adapted to actuate said detonator when ionized, means including the cathode-grid electrode circuit of an electron tube having cathode, control grid, and plate electrodes for developing a voltage which is a function of the amplitude of said amplified beat frequency signal for controlling the gain of said amplifier, means including the serial arrangement of a linear and a nonlinear impedance in the cathode-plate electrode circuit of said electron tube for developing from said high frequency and said reflected signals a voltage for biasing said gas-filled tube below its starting voltage, high frequency choke coil means in said cathodegrid electrode circuit for isolating said automatic volume control bias developing means from the high frequency bias developing means, and means for coupling the output of said amplifier to the grid of said gas-filled tube.
 4. In a radio-controlled promixity fuze having an antenna adapted to radiate and receive radio frequency energy, a detector coupled to said antenna and adapted to oscillate at radio frequency and to detect the difference in frequency between the radiated signal and the signal reflected from a target approached by said fuze, an amplifier peaked at said difference in frequency and adapted to by-pass said radio frequency to ground, an electrically-actuated detonator adapted to initiate the explosion of said fuze, and a grid-controlled gas-filled discharge tube adapted to actuate said detonator when energized; circuit means for providing a voltage for biasing said gas-filled tube below its starting voltage and foR providing an automatic volume control bias voltage for said amplifier, including the serial arrangement of a resistance and a radio frequency choke coil in the cathode-grid circuit of an electron tube having cathode, grid, and plate electrodes, the output of said amplifier being coupled to the grid electrode of said electron tube through said choke coil and being capacitively coupled to the control grid of said gas-filled tube, a linear and a nonlinear impedance in series in the cathode-plate circuit of said electron tube, the grid of said gas-filled tube being coupled to the junction of said linear and said nonlinear impedances, and means for coupling a portion of the radio-frequency energy from said oscillating detector across said cathode-plate circuit.
 5. In a radio-controlled proximity fuze in which a high frequency signal is generated and radiated and received after reflection from a target approached by said fuze and a beat frequency signal derived from the radiated and reflected signals triggers a gas-filled discharge tube to initiate the detonation of the fuze, means including a rectifier and a nonlinear impedance in the output circuit of said rectifier for deriving from said high frequency and said reflected signals a substantially constant voltage for biasing said gas-filled tube to its deionized state.
 6. In a radio-controlled proximity fuze in which a high frequency signal is generated and radiated and received after reflection from a target approached by said fuze and a low frequency signal derived from heterodyning said radiated and reflected signals is amplified in an amplifier and triggers a gas-filled discharge tube to initiate the detonation of said fuze, means including the cathode-plate circuit of an electron tube and a nonlinear impedance in said cathode-plate circuit for deriving from said high frequency and said reflected signals a voltage for biasing the gas-filled tube to its deionized state, means including the cathode-grid circuit of said electron tube for developing a voltage which is a function of the amplitude of said amplified low frequency signal for controlling the gain of said amplifier, and means for isolating said high frequency voltage deriving means from said low frequency voltage developing means.
 7. In a fuze in accordance with claim 6 and including means responsive to a selected amplitude and number of cycles of said amplified low frequency signal for ionizing said gas-filled tube. 